This research is addressed to the prenatal and postnatal experimental background to the infant's postnatal auditory and visual attachment to the maternal parent. These aims are achieved by analyzing the maternal-infant social bond in the laboratory using bird (duck) embryos and hatchlings. For the next project period the auditory experiments are focused on the experiential factors disposing the embryo and hatchling to malleability (susceptibility to acquiring a preference for an alien species maternal call) and the usual experiential safeguards buffering the individual against such influences. Does social rearing with siblings promote malleability, whereas the embryo's exposure to its own voice (self-stimulation) normally render it nonmalleable? Are hole-nesting species, whose species-specific auditory responsiveness is dependent upon hearing sib vocalizations, more malleable than ground-nesting species (in which auditory self-stimulation is effective)? In the visual realm, we are going to determine why social interaction with sibs sometimes enhances, and at other times interferes with, maternal imprinting. In addition we will reopen the question of whether ground-nesting species (mallard) are more capable of visual imprinting than hole-nesting species (wood duck, mandarin) using, for the first time, species-typical auditory and visual maternal stimulation with the hole-nesting as well as the ground-nesting species. Finally, to determine the experiential contribution to the early dominance of maternal auditory over maternal visual stimulation, ducklings will be muted and deprived of auditory experience to see if such deprivation does away with the early auditory dominance (maternal call) over visually imprinted maternal preferences.